Strained metal silicon nitride films and method of forming

ABSTRACT

A method for forming a strained metal nitride film and a semiconductor device containing the strained metal nitride film. The method includes exposing a substrate to a gas containing a metal precursor, exposing the substrate to a gas containing a silicon precursor, exposing the substrate to a gas containing a nitrogen precursor activated by a plasma source at a first level of plasma power and configured to react with the metal precursor or the silicon precursor with a first reactivity characteristic, and exposing the substrate to a gas containing the nitrogen precursor activated by the plasma source at a second level of plasma power different from the first level and configured to react with the metal precursor or the silicon precursor with a second reactivity characteristic such that a property of the metal silicon nitride film formed on the substrate changes to provide the strained metal silicon nitride film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser.No. 11/730,288. Publication No. US2008-0242116-A1, entitled “METHOD OFFORMING STRAINED SILICON NITRIDE FILMS AND A DEVICE CONTAINING SUCHFILMS,”filed on even date herewith; co-pending U.S. patent applicationSer. No. 11/730,342, Publication No. US2008 -0241555-A1, entitled“STRAINED METAL NITRIDE FILMS AND METHOD OF FORMING,”filed on even dateherewith; co-pending U.S. patent application Ser. No. 11/730,340.Publication No. US2008-0241382-A1, entitled “STRAINED METAL NITRIDEFILMS AND METHOD OF FORMING,”filed on even date herewith; co-pendingU.S. Pat. application Ser. No. 11/730,334. Publication No.US2008-0241388-A1, entitled “STRAINED METAL SILICON NITRIDE FILMS ANDMETHOD OF FORMING,”filed on even date herewith; and co-pending U.S.patent application Ser. No. 11/529,380,Publication No.US2008-0081470-A1, entitled “A METHOD OF FORMING STRAINED SILICONNITRIDE FILMS AND A DEVICE CONTAINING SUCH FILMS,”filed on Sep. 29,2006. The entire contents of these applications are herein incorporatedby reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to semiconductor processing, and moreparticularly to methods of forming strained metal silicon nitride filmsand semiconductor devices containing these strained films.

BACKGROUND OF THE INVENTION

Nitride-based films are widely used in semiconductor devices andultra-large-scale integrated (ULSI) circuits. For example, nitride filmshave been widely used in semiconductor devices as diffusion barriers fordopants and metals, as an etch-stop film during etching of finefeatures, as a final passivation film for encapsulation of fabricateddevices, and as electrodes in capacitor and metal-oxide semiconductorfield-effect transistor (MOSFET) structures, among many other uses.Nitride films can be deposited at low pressure or at atmosphericpressure using a variety of processing systems and process gases.

Recent innovations to improve complementary metal oxide semiconductor(CMOS) transistor performance have created an industry need for strainedfilms that are compatible with current ULSI integration techniques. Inparticular, channel carrier mobility for negative metal oxidesemiconductor (NMOS) transistors can be increased through introductionof tensile uniaxial or biaxial strain on a channel region of a MOStransistor. Typically, this has been accomplished by deposition ofhighly tensile strained silicon nitride films that are compatible withexisting fabrication processes. With the advent of metal gate stacks,the strain imparted in the channel using stressed silicon nitride linerfilms over the MOSFET will be decreased due to the higher modulus of themetallic films. One proposed solution to this problem is to use stressedfilms within the gate stack, so that the stressed film is more proximateto the channel, thus increasing the imparted strain.

SUMMARY OF THE INVENTION

One embodiment of the invention includes a method of depositing astrained metal silicon nitride film on a substrate in a process chamber,including exposing the substrate to a gas including a metal precursor;exposing the substrate to a gas including a silicon precursor; andexposing the substrate to a gas including a nitrogen precursor activatedby a plasma source at a first level of plasma power and configured toreact with the metal precursor or the silicon precursor with a firstreactivity characteristic. Also included is exposing the substrate to agas including the nitrogen precursor activated by the plasma source at asecond level of plasma power different from the first level andconfigured to react with the metal precursor or the silicon precursorwith a second reactivity characteristic such that a property of themetal silicon nitride film formed on the substrate changes to providethe strained metal silicon nitride film.

According to another embodiment, the method includes a) exposing thesubstrate to a gas pulse including the metal precursor; b) exposing thesubstrate to a gas pulse including the nitrogen precursor activated bythe plasma source at the first level of plasma power; and c) exposingthe substrate to a gas pulse including the silicon precursor. Alsoincluded is exposing, the substrate to a gas pulse including thenitrogen precursor activated by the plasma source at the second level ofplasma power; and e) repeating steps a)-d) a predetermined number oftimes.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 schematically shows a cross-sectional view of a device containinga strained metal nitride or metal silicon nitride film according toembodiments of the invention;

FIGS. 2A-2B illustrate processing systems for forming strained metalnitride or metal silicon nitride films according to embodiments of theinvention;

FIGS. 3A-3E are process flow diagrams for forming strained metal nitridefilms according to embodiments of the present invention;

FIGS. 4A-4E are process flow diagrams for forming strained metal nitridefilms according to embodiments of the present invention;

FIGS. 5A and 5B show power graphs depicting different levels of plasmapower coupled to a process chamber according to embodiments of theinvention;

FIGS. 6A-6E are process flow diagrams for forming strained metal siliconnitride films according to embodiments of the present invention; and

FIGS. 7A-7E are process flow diagrams for forming strained metal siliconnitride films according to embodiments of the present invention.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

Embodiments of the invention describe processing methods to depositstrained metal nitride and metal silicon nitride films with goodthickness and uniformity control. In the case of metal nitride films,the processing methods utilize a metal precursor and one or morenitrogen precursors having a difference in reactivity towards the metalprecursor, thereby depositing metal nitride films having a densitygradient across the film thickness that creates tensile or compressivestrain within the deposited film. In the case of metal silicon nitridefilms, the processing methods utilize a metal precursor, a siliconprecursor, and one or more nitrogen precursors having a difference inreactivity towards the metal precursor or the silicon precursor.

According to one embodiment of the invention, a difference in heat offormation (ΔH) of different nitrogen precursors may be utilized toachieve a difference in reactivity towards a metal precursor and/or asilicon precursor. NH₃ (ΔH=−45.9 kJ/mol) and N₂H₄ (ΔH=95.35 kJ/mol) areexamples of nitrogen precursors with a large, difference in heat offormation. For example, using the same or similar processing conditions,a first metal nitride film portion deposited using N₂H₄ will have adifferent deposition rate and different film density than a second metalnitride film portion deposited using NH₃ onto the first metal nitridefilm portion. Variations in density across the thickness of an amorphousor crystalline film such as TiN will result in TiN film strain due tovariations in coefficient of thermal expansion created across the TiNfilm. In the case of metal silicon nitride films, this difference indensity may be further affected by altering the silicon precursor or theprocessing conditions during processing.

Alternately, a difference in reactivity may be achieved by varyingplasma activation of a nitrogen precursor during processing. Forexample, the reactivity may be controlled by the type of plasmaactivation and the level of plasma power used for the activation.According to embodiments of the invention, plasma activation may beaccomplished using a direct plasma source within the process chamber orusing a remote plasma source.

In one example, embodiments of the invention may be utilized for forminga strained metal nitride or metal silicon nitride film located betweenmaterials with very different coefficients of thermal expansion, therebyincreasing adhesion between the materials and decreasing the possibilityof delamination during thermal cycling.

Embodiments of the invention may utilize atomic layer deposition (ALD),plasma enhanced ALD (PEALD), chemical vapor depositions (CVD), plasmaenhanced CVD (PECVD), and pulsed CVD methods for depositing strainedmetal nitride and metal silicon nitride films. These deposition methodsare well known methods for depositing a wide variety of materials. ALDis a CVD related film deposition method that uses sequential saturativesurface reactions. In ALD, pulses of the gaseous precursors arealternately exposed to the substrate. In CVD, an uninterrupted flow ofthe gaseous precursors is exposed to the substrate, and in pulsed CVD,the flow of the gaseous precursors is periodically interrupted duringthe film deposition. In PEALD and PECVD, plasma excitation is utilizedduring at least a portion of the deposition process. The use of ALD,PEALD, CVD, PECVD, and pulsed CVD processing allows for varying thenitrogen precursor, ratio of nitrogen precursors, and/or processingconditions during the film deposition. In one example, the nitrogenprecursor can be varied from N₂H₄ to a combination of N₂H₄ and NH₃, topure NH₃, during CVD and pulsed CVD processing. In another example, thenumber of N₂H₄ gas pulses versus NH₃ gas pulses can be varied during ALDor PEALD processing. In another example, a level of plasma power used toactivate the N₂H₄ or NH₃ gas can be varied during PEALD or PECVDprocessing. In yet another example, a dilution gas may be used incombination with plasma power to affect reactivity.

As used herein, metal nitride films refer to films containing a metalelement (or multiple metal elements) and nitrogen (N) as the majorelements, where the elemental composition of the metal nitride films canbe varied over wide ranges of atomic concentrations for the metal ormetals and N. Metal silicon nitride films refer to films containing ametal element (or multiple metal elements), silicon (Si) and nitrogen(N) as the major elements, where the elemental composition of the metalsilicon nitride films can be varied over wide ranges of atomicconcentrations for the metal or metals, Si and/or N. Furthermore, themetal nitride and metal silicon nitride films may contain impuritiessuch as carbon (C), oxygen (O), halogen (e.g., chlorine (Cl)), andhydrogen (H), that may become incorporated into the films during thesubstrate processing or during substrate transfer. The terms “film” and“layer”are used interchangeably herein to refer to a material depositedor formed on a substrate.

Referring now to the drawings, FIG. 1 schematically shows across-sectional view of a device containing a strained metal nitride ormetal silicon nitride film according to an embodiment of the invention.The strained nitride film 118 is disposed in a MOS device 100. Thedevice 100, as shown, includes a substrate 112 having doped regions 113and 114 (e.g., source and drain), a gate stack 120, a spacer 121, and aliner 122. The substrate 112 can for example be a Si, Ge, Si/Ge, or GaAssubstrate wafer. The substrate 112 can be of any size, for example, a200 mm substrate, a 300 mm substrate, or an even larger substrate.

The gate stack 120 includes a dielectric film 116 on the channel region115. The dielectric layer 116 can for example include a SiO₂layer, a SiNlayer, a SiON layer, or a combination thereof, or any other appropriatedielectric-material. The dielectric film 116 can further include ahigh-dielectric constant (high-k) dielectric material. The high-kdielectric material can for example include metal oxides and theirsilicates, including Ta₂O₅, TiO₂, ZrO₂, Al₂O₃, Y₂O₃, HfO_(x)N_(y),HfSiO_(x)N_(y), HfSiO_(x), HfO₂, ZrO₂, ZrSiO_(x), ZrO_(x)N_(y),ZrSiO_(x)N_(y), TaSiO_(x), SrO_(x), SrSiO_(x), LaO_(x), LaSiO_(x),YO_(x), YSiO_(x), or BaO, or combinations of two or more thereof.

In one embodiment of the invention, a conductive film 117 (e.g., a gateelectrode film) is formed on the dielectric film 116, and a strainedmetal nitride film or metal silicon nitride film 118 is formed on theconductive film 117 to impart strain to the channel region 115. A caplayer 119 can be positioned at the top of the gate stack 120 to protectthe gate stack 120 and improve electrical contact to the gate stack 120.The cap layer 119 can, for example, include one or more of a SiN layer,a W layer, a WSi_(x) layer, a CoSi_(x) layer, a NiSi_(x) layer or apolycrystalline or amorphous Si layer.

In one example, the conductive layer 117 can be tantalum nitride (TaN),and the strained metal nitride film 118 can contain titanium nitride(TiN). The gate stack 120 may include different and fewer or more filmsor layers than shown in FIG. 1. In one example, film 117 and film 118may be composed of the same metal nitride or metal silicon nitride filmwith a vertical density gradient formed according to embodiments of theinvention. FIG. 1 further shows that spacer 121 is formed on either sideof the gate stack 120 in order to protect the gate stack 120 from damageand ensure electrical performance of the gate. In addition, the spacer121 can be used as a hard mask for the formation of the source and drain113, 114 of the MOS device 100. Alternately, in one embodiment, morethan one spacer 121 may be used.

In one embodiment, the device 100 can be a NMOS device where thestrained metal nitride or metal silicon nitride film 118 increaseschannel carrier mobility through introduction of a tensile stress on thechannel region 115. The strained nitride film 118 can also serve as aconductive film for improving electrical contact to the device 100.

In another embodiment, the device 100 can be a PMOS device where thestrained metal nitride film 118 increases channel carrier mobilitythrough introduction of a compressive stress on the channel region 115,thus enhancing transistor mobilities and hence overall transistorperformance. The strained metal nitride film 118 can also serve as aconductive film for improving electrical contact to the device 100.

FIG. 2A illustrates a processing system 1 for forming strained metalnitride and/or metal silicon nitride films according to embodiments ofthe invention. The processing system 1 can be configured to perform anALD process, a CVD process, or a pulsed CVD process. The processingsystem 1 includes a process chamber 10 having a substrate holder 20configured to support a substrate 25, upon which the strained film isformed. The process chamber 10 further contains an upper assembly 30(e.g., a showerhead) configured for introducing process gases into theprocess chamber 10, a metal precursor supply system 40, a first nitrogenprecursor supply system 42, a second nitrogen precursor supply system44, a silicon precursor supply system 46, a purge gas supply system 48,and an auxiliary gas supply system 50. Furthermore, the processingsystem 1 includes a substrate temperature control system 60 coupled tosubstrate holder 20 and configured to elevate and control thetemperature of the substrate 25.

In FIG. 2A, singular processing elements (10, 20, 30, 40, 42, 44, 46,48, 50, and 60) are shown, but this is not required for the invention.The processing system 1 can include any number of processing elementshaving any number of controllers associated with them in addition toindependent processing elements. The controller 70 can be used toconfigure any number of processing elements. (10, 20, 30, 40, 42, 44,46, 48, 50, and 60), and the controller 70 can collect, provide,process, store, and display data from the processing elements. Thecontroller 70 can comprise a number of applications for controlling oneor more of the processing elements. For example, controller 70 caninclude a graphic user interface (GUI) component (not shown) that canprovide easy to use interfaces that enable a user to monitor and/orcontrol one or more processing elements.

Still referring to FIG. 2A, the processing system 1 may be configured toprocess 200 mm substrates, 300 mm substrates, or larger-sizedsubstrates. In fact, it is contemplated that the deposition system maybe configured to process substrates, wafers, or LCDs regardless of theirsize, as would be appreciated by those skilled in the art. Therefore,while aspects of the invention will be described in connection with theprocessing of a semiconductor substrate, the invention is not limitedsolely thereto. Alternately, a batch processing system capable ofprocessing multiple substrates simultaneously may be utilized fordepositing the strained films described in the embodiments of theinvention.

Still referring to FIG. 2A, the purge gas supply system 48 is configuredto introduce a purge gas to process chamber 10. For example, theintroduction of purge gas may occur between introduction of pulses of ametal precursor, a silicon precursor, a first nitrogen precursor, and asecond nitrogen precursor gas to the process chamber 10. The purge gascan comprise an inert gas, such as a noble gas (i.e., He, Ne, Ar, Kr,Xe), nitrogen (N₂), or hydrogen (H₂).

The substrate temperature control system 60 contains temperature controlelements, such as a cooling system including a re-circulating coolantflow that receives heat from substrate holder 20 and transfers heat to aheat exchanger system (not shown), or when heating, transfers heat fromthe heat exchanger system to the substrate holder. Additionally, thetemperature control elements can include heating/cooling elements, suchas resistive heating elements, or thermoelectric heaters/coolers, whichcan be included in the substrate holder 20, as well as the chamber wallof the process chamber 10 and any other component within the processingsystem 1. The substrate temperature control system 60 can, for example,be configured to elevate and control the substrate temperature from roomtemperature to approximately 600° C., or higher. In another example, thesubstrate temperature can, for example, range from approximately 150° C.to 350° C. It is to be understood, however, that the temperature of thesubstrate is selected based on the desired temperature for causingdeposition of a particular nitride film on the surface of a givensubstrate.

In order to improve the thermal transfer between substrate 25 andsubstrate holder 20, substrate holder 20 can include a mechanicalclamping system, or an electrical clamping system, such as anelectrostatic clamping system, to affix substrate 25 to an upper surfaceof substrate holder 20. Furthermore, substrate holder 20 can furtherinclude a substrate backside gas delivery system configured to introducegas (e.g., helium (He)) to the back-side of substrate 25 in order toimprove the gas-gap thermal conductance between substrate 25 andsubstrate holder 20. Such a system can be utilized when temperaturecontrol of the substrate is required at elevated or reducedtemperatures. For example, the substrate backside gas system cancomprise a two-zone gas distribution system, wherein He gas-gap pressurecan be independently varied between the center and the edge of substrate25.

Furthermore, the process chamber 10 is further coupled to a pressurecontrol system 32, including a vacuum pumping system 34 and a valve 36,through a duct 38, wherein the pressure control system 32 is configuredto controllably evacuate the process chamber 10 to a pressure suitablefor forming the nitride film on substrate 25, and suitable for use ofthe precursor gases. The vacuum pumping system 34 can include aturbo-molecular vacuum pump (TMP) or a cryogenic pump capable of apumping speed up to about 5000 liters per second (and greater) and valve36 can include a gate valve for throttling the chamber pressure.Moreover, a device for monitoring chamber pressure (not shown) can becoupled to the process chamber 10. The pressure control system 32 can,for example, be configured to control the process chamber pressurebetween about 0.1 Torr and about 100 Torr during deposition of thestrained films. For example, the process chamber pressure can be betweenabout 0.1 Torr and about 10 Torr, or between about 0.2 Torr and about 3Torr.

The metal precursor supply system 40, first nitrogen precursor supplysystem 42, second nitrogen precursor gas supply system 44, siliconprecursor supply system 46, a purge gas supply system 48, and auxiliarygas supply system 50 can include one or more pressure control devices,one or more flow control devices, one or more filters, one or morevalves, and/or one or more flow sensors. The flow control devices caninclude pneumatic driven valves, electromechanical (solenoidal) valves,and/or high-rate pulsed gas injection valves. According to embodimentsof the invention, gases may be sequentially and alternately pulsed intothe process chamber 10. An exemplary pulsed gas injection system isdescribed in greater detail in pending U.S. Patent ApplicationPublication No. 2004/0123803.

In exemplary ALD and PEALD processes, the length of each gas pulse can,for example, be between about 0.1 sec and about 100 sec. Alternately,the length of each gas pulse can be between about 1 sec and about 10sec. Exemplary gas pulse lengths for metal precursors can be between 0.3and 3 sec, for example 1 sec. Exemplary gas pulse lengths for a nitrogenprecursor and a silicon precursor can be between 0.1 and 3 sec, forexample 0.3 sec. Exemplary purge gas pulses can be between 1 and 20 sec,for example 3 sec.

Still referring to FIG. 2A, controller 70 can comprise a microprocessor,memory, and a digital I/O port capable of generating control voltagessufficient to communicate and activate inputs to the processing system 1as well as monitor outputs from the processing system 1. Moreover, thecontroller 70 may be coupled to and may exchange information with theprocess chamber 10, substrate holder 20, upper assembly 30, metalprecursor supply system 40, first nitrogen precursor supply system 42,second nitrogen precursor gas supply system 44, silicon precursor supplysystem 46, purge gas supply system 48, auxiliary gas supply system 50,substrate temperature control system 60, and pressure control system 32.For example, a program stored in the memory may be utilized to activatethe inputs to the aforementioned components of the processing system 1according to a process recipe in order to perform a deposition process.One example of the controller 70 is a DELL PRECISION WORKSTATION 610™,available from Dell Corporation, Austin, Tex.

However, the controller 70 may be implemented as a general purposecomputer system that performs a portion or all of the microprocessorbased processing steps of the invention in response to a processorexecuting one or more sequences of one or more instructions contained ina memory. Such instructions may be read into the controller memory fromanother computer readable medium, such as a hard disk or a removablemedia drive. One or more processors in a multi-processing arrangementmay also be employed as the controller microprocessor to execute thesequences of instructions contained in main memory. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions. Thus, embodiments are notlimited to any specific combination of hardware circuitry and software.The controller 70 can be coupled to one or more additionalcontrollers/computers (not shown), and controller 70 can obtain setupand/or configuration information from an additional controller/computer.

The controller 70 includes at least one computer readable medium ormemory, such as the controller memory, for holding instructionsprogrammed according to the teachings of the invention and forcontaining data structures, tables, records, or other data that may benecessary to implement, the present invention. Examples of computerreadable media are compact discs, hard disks, floppy disks, tape,magneto-optical disks, PROMs (EPROM, EEPROM, flash EPROM), DRAM, SRAM,SDRAM, or any other magnetic medium, compact discs (e.g., CD-ROM), orany other optical medium, punch cards, paper tape, or other physicalmedium with patterns of holes, a carrier wave (described below), or anyother medium from which a computer can read.

Stored on any one or on a combination of computer readable media,resides software for controlling the controller 70, for driving a deviceor devices for implementing the invention, and/or for enabling thecontroller to interact with a human user. Such software may include, butis not limited to, device drivers, operating systems, development tools,and applications software. Such computer readable media further includesthe computer program product of the present invention for performing allor a portion (if processing is distributed) of the processing performedin implementing embodiments of the invention.

The computer code devices may be any interpretable or executable codemechanism, including but not limited to scripts, interpretable programs,dynamic link libraries (DLLs), Java classes, and complete executableprograms. Moreover, parts of the processing of the present invention maybe distributed for better performance, reliability, and/or cost.

The term “computer readable medium” as used herein refers to any mediumthat participates in providing instructions to the processor of thecontroller 70 for execution. A computer readable medium may take manyforms, including but not limited to, non-volatile media, volatile media,and transmission media. Non-volatile media includes, for example,optical, magnetic disks, and magneto-optical disks, such as the harddisk or the removable media drive. Volatile media includes dynamicmemory, such as the main memory. Moreover, various forms of computerreadable media may be involved in carrying out one or more sequences ofone or more instructions to processor of controller for execution. Forexample, the instructions may initially be carried on a magnetic disk ofa remote computer. The remote computer can load the instructions forimplementing all or a portion of the present invention remotely into adynamic memory and send the instructions over a network to thecontroller 70.

The controller 70 may be locally located relative to the processingsystem 1, or it may be remotely located relative to the processingsystem 1. For example, the controller 70 may exchange data with theprocessing system 1 using at least one of a direct connection, anintranet, the Internet and a wireless connection. The controller 70 maybe coupled to an intranet at, for example, a customer site (i.e., adevice maker, etc.), or it may be coupled to an intranet at, forexample, a vendor site (i.e., an equipment manufacturer). Additionally,for example, the controller 70 may be coupled to the Internet.Furthermore, another computer (i.e., controller, server, etc.) mayaccess, for example, the controller 70 to exchange data via at least oneof a direct connection, an intranet, and the Internet. As also would beappreciated by those skilled in the art, the controller 70 may exchangedata with the processing system 1 via a wireless connection.

FIG. 2B illustrates a processing system 2 for forming strained metalnitride and/or metal silicon nitride films according to embodiments ofthe invention. The processing system 2 can be configured to perform anPEALD or a PECVD process. The processing system 2 is similar to theprocessing system 1 described in FIG. 2A, but further includes a plasmageneration system configured to generate a plasma during at least aportion of the gas exposures in the process chamber 10. According to oneembodiment of the invention, plasma excited nitrogen may be formed froma nitrogen-containing gas containing N₂, NH₃, or N₂H₄, or C₁-C₁₀alkylhydrazine compounds, or a combination thereof.

The plasma generation system includes a first power source 52 coupled tothe process chamber 10, and configured to couple power to gasesintroduced into the process chamber 10. The first power source 52 may bea variable power source and may include a radio frequency (RF) generatorand an impedance match network, and may further include an electrodethrough which RF power is coupled to the plasma in process chamber 10.The electrode can be formed in the upper assembly 31, and it can beconfigured to oppose the substrate holder 20. The impedance matchnetwork can be configured to optimize the transfer of RF power from theRF generator to the plasma by matching the output impedance of the matchnetwork with the input impedance of the process chamber 10, includingthe electrode, and plasma. For instance, the impedance match networkserves to improve the transfer of RF power to plasma in process chamber10 by reducing the reflected power. Match network topologies (e.g.L-type, π-type, T-type, etc.) and automatic control methods are wellknown to those skilled in the art.

Alternatively, the first power source 52 may include a RF generator andan impedance match network, and may further include an antenna, such asan inductive coil, through which RF power is coupled to a plasma inprocess chamber 10. The antenna can, for example, include a helical orsolenoidal coil, such as in an inductively coupled plasma source orhelicon source, or it can, for example, include a flat coil as in atransformer coupled plasma source.

Still alternatively, the first power source 52 may include a microwavefrequency generator, and may further include a microwave antenna andmicrowave window through which microwave power is coupled to a plasma inprocess chamber 10. The coupling of microwave power can be accomplishedusing electron cyclotron resonance (ECR) technology, or it may beemployed using surface wave plasma technology, such as a slotted planeantenna (SPA), as described in U.S. Pat. No. 5,024,716, the entirecontent of which is incorporated herein by reference.

According to one embodiment of the invention, the processing system 2includes a substrate bias generation system configured to generate orassist in generating a plasma (through biasing of substrate holder 20)during at least a portion of the alternating introduction of the gasesto the process chamber 10. The substrate bias system can include asubstrate power source 54 coupled to the process chamber 10, andconfigured to couple power to the substrate 25. The substrate powersource 54 may include a RF generator and an impedance match network, andmay further include an electrode through which RF power is coupled tosubstrate 25. The electrode can be formed in substrate holder 20. Forinstance, substrate holder 20 can be electrically biased at a RF voltagevia the transmission of RF power from a RF generator (not shown) throughan impedance match network (not shown) to substrate holder 20. A typicalfrequency for the RF bias can range from about 0.1 MHz to about 100 MHz,and can be 13.56 MHz. RF bias systems for plasma processing are wellknown to those skilled in the art. Alternatively, RF power is applied tothe substrate holder electrode at multiple frequencies. Although theplasma generation system and the substrate bias system are illustratedin FIG. 2B as separate entities, they may indeed comprise one or morepower sources coupled to substrate holder 20.

In addition, the processing system 2 includes a remote plasma system 56for providing and remotely plasma exciting a gas (e.g., a nitrogenprecursor) prior to flowing the plasma excited gas into the processchamber 10 where it is exposed to the substrate 25. The remote plasmasystem 56 can, for example, contain a microwave frequency generator.

Examples of metal precursors, silicon precursors, and nitrogenprecursors that may be utilized in embodiments of the invention todeposit strained metal nitride and metal silicon nitride films will nowbe described. As those skilled in the art will readily recognize, othermetal precursors, silicon precursors, and nitrogen precursors notdescribed below, but suitable for film deposition, may be utilized.

Embodiments of the invention may use metal precursors selected from thegroups of volatile metal precursors suitable for depositing stable metalnitride or metal silicon nitride films. The metal precursor can, forexample contain a metal element selected from alkaline earth elements,rare earth elements, Group III, Group IIIB, Group IVB, Group VB, andGroup VIB of the Periodic Table, or a combination of two or morethereof.

Embodiments of the invention may utilize a wide variety of differentalkaline earth precursors. For example, many alkaline earth precursorshave the formula:ML¹L²D_(x)where M is an alkaline earth metal element selected from the group ofberyllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium(Ba). L¹ and L² are individual anionic ligands, and D is a neutral donorligand where x can be 0, 1, 2, or 3. Each L¹, L² ligand may beindividually selected from the groups of alkoxides, halides, aryloxides,amides, cyclopentadienyls, alkyls, silyls, amidinates, β-diketonates,ketoiminates, silanoates, and carboxylates. D ligands may be selectedfrom groups of ethers, furans, pyridines, pyroles, pyrolidines, amines,crown ethers, glymes, and nitriles.

Examples of L group alkoxides include tert-butoxide, iso-propoxide,ethoxide, 1-methoxy-2,2-dimethyl-2-propionate (mmp),1-dimethylamino-2,2′-dimethyl-propionate, amyloxide, and neo-pentoxide.Examples of halides include fluoride, chloride, iodide, and bromide.Examples of aryloxides include phenoxide and 2,4,6-trimethylphenoxide.Examples of amides include bis(trimethylsilyl)amide di-tert-butylamide,and 2,2,6,6-tetramethylpiperidide (TMPD). Examples of cyclepentadienylsinclude cyclopentadienyl, 1-methylcyclopentadienyl,1,2,3,4-tetramethylcyclopentadienyl, 1-ethylcyclopentadienyl,pentamethylcyclopentadienyl, 1-iso-propylcyclopentadienyl,1-n-propylcyclopentadienyl, and 1-n-butylcyclopentadienyl. Examples ofalkyls include bis(trimethylsilyl)methyl, tris(trimethylsilyl)methyl,and trimethylsilylmethyl. An example of a silyl is trimethylsilyl.Examples of amidinates include N,N′-di-tert-butylacetamidinate,N,N′-di-iso-propylacetamidinate,N,N′-di-isopropyl-2-tert-butylamidinate, andN,N′-di-tert-butyl-2-tert-butylamidinate. Examples of β-diketonatesinclude 2,2,6,6-tetramethyl-3,5-heptanedionate (THD),hexafluoro-2,4-pentanedionate (hfac), and6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate (FOD). Anexample of a ketoiminate is 2-iso-propylimino-4-pentanonate. Examples ofsilanoates include tri-tert-butylsiloxide and triethylsiloxide. Anexample of a carboxylate is 2-ethylhexanoate.

Examples of D ligands include tetrahydrofuran, diethylether,1,2-dimethoxyethane, diglyme, triglyme, tetraglyme, 12-Crown-6,10-Crown-4, pyridine, N-methylpyrolidine, triethylamine, trimethylamine,acetonitrile, and 2,2-dimethylpropionitrile.

Representative examples of alkaline earth precursors include:

Be precursors: Be(N(SiMe₃)₂)₂, Be(TMPD)₂, and BeEt₂.

Mg precursors: Mg(N(SiMe₃)₂)₂, Mg(TMPD)₂, Mg(PrCp)₂, Mg(EtCp)₂, andMgCp₂.

Ca precursors: Ca(N(SiMe₃)₂)₂, Ca(iPr₄Cp)₂, and Ca(Me₅Cp)₂.

Sr precursors: Bis(tert-butylacetamidinato)strontium (TBAASr),Sr(N(SiMe₃)₂)₂, Sr(THD)₂, Sr(THD)₂(tetraglyme), Sr(iPr₄Cp)₂,Sr(iPr₃Cp)₂, and Sr(Me₅Cp)₂.

Ba precursors: Bis(tert-butylacetamidinato)barium (TBAABa),Ba(N(SiMe₃)₂)₂, Ba(THD)₂, Ba(THD)₂(tetraglyme), Ba(iPr₄Cp)₂, Ba(Me₅Cp)₂,and Ba(nPrMe₄Cp)₂.

Representative examples of Group IVB precursors include: Hf(OtBu)₄(hafnium tert-butoxide, HTB), Hf(NEt₂)₄ (tetrakis(diethylamido)hafnium,TDEAH), Hf(NEtMe)₄ (tetrakis(ethylmethylamido)hafnium, TEMAH), Hf(NMe₂)₄(tetrakis(dimethylamido)hafnium, TDMAH), Zr(OtBu)₄ (zirconiumtert-butoxide, ZTB), Zr(NEt₂)₄ (tetrakis(diethylamido)zirconium, TDEAZ),Zr(NMeEt)₄ (tetrakis(ethylmethylamido)zirconium, TEMAZ), Zr(NMe₂)₄(tetrakis(dimethylamido)zirconium, TDMAZ), Hf(mmp)₄, Zr(mmp)₄, Ti(mmp)₄,HfCl₄, ZrCl₄, TiCl₄, Ti(NiPr₂)₄, Ti(NiPr₂)₃,tris(N,N′-dimethylacetamidinato)titanium, ZrCp₂Me₂, Zr(tBuCp)₂Me₂,Zr(NiPr₂)₄, Ti(OiPr)₄, Ti(OtBu)₄ (titanium tert-butoxide, TTB),Ti(NEt₂)₄ (tetrakis(diethylamido)titanium, TDEAT), Ti(NMeEt)₄(tetrakis(ethylmethylamido)titanium, TEMAT), Ti(NMe₂)₄(tetrakis(dimethylamido)titanium, TDMAT), and Ti(THD)₃(tris(2,2,6,6-tetramethyl-3,5-heptanedionato)titanium).

Representative examples of Group VB precursors include: Ta(NMe₂)₅(pentakis(dimethylamido)tantalum, PDMAT), Ta(NEtMe)₅(pentakis(ethylmethylamido)tantalum, PEMAT), (tBuN)Ta(NMe₂)₃(tert-butylimido tris(dimethylamido)tantalum, TBTDMT), (tBuN)Ta(NEt₂)₃(tert-butylimido tris(diethylamido)tantalum, TBTDET), (tBuN)Ta(NEtMe)₃(tert-butylimido tris(ethylmethylamido)tantalum, TBTEMT),(EtMe₂CN)Ta(NMe₂)₃ (tert-amylimido tris(dimethylamido)tantalum,TAIMATA), (iPrN)Ta(NEt₂)₃ (iso-propylimino tris(diethylamido)tantalum,IPTDET), Ta₂(OEt)₁₀ (tantalum penta-ethoxide, TAETO),(Me₂NCH₂CH₂O)Ta(OEt)₄ (dimethylaminoethoxy tantalum tetra-ethoxide,TATDMAE), TaCl₅ (tantalum penta-chloride), Nb(NMe₂)₅(pentakis(dimethylamido)niobium, PDMANb), Nb₂(OEt)₁₀ (niobiumpenta-ethoxide, NbETO), (tBuN)Nb(NEt₂)₃ (tert-butyliminotris(diethylamido)niobium, TBTDEN), and NbCl₅ (niobium penta-chloride).

Representative examples of Group VIB precursors include: Cr(CO)₆(chromium hexacarbonyl), Mo(CO)₆ (molybdenum hexacarbonyl), W(CO)₆(tungsten hexacarbonyl), WF₆ (tungsten hexafluoride), and(tBuN)₂W(NMe₂)₂ (bis(tert-butylimido)bis(dimethylamido)tungsten, BTBMW).

Embodiments of the inventions may utilize a wide variety of differentrare earth precursors. For example, many rare earth precursors have theformula:ML¹L²L³D_(x)where M is a rare earth metal element selected from the group ofscandium (Sc), yttrium (Y), lutetium (Lu), lanthanum (La), cerium (Ce),praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu),gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium(Er), thulium (Tm), and ytterbium (Yb). L¹, L², L³ are individualanionic ligands, and D is a neutral donor ligand where x can be 0, 1, 2,or 3. Each L¹, L², L³ ligand may be individually selected from thegroups of alkoxides, halides, aryloxides, amides, cyclopentadienyls,alkyls, silyls, amidinates, β-diketonates, ketoiminates, silanoates, andcarboxylates. D ligands may be selected from groups of ethers, furans,pyridines, pyroles, pyrolidines, amines, crown ethers, glymes, andnitriles.

Examples of, L groups and D ligands are identical to those presentedabove for the alkaline earth precursor formula.

Representative, examples of rare earth precursors include:

Y precursors: Y(N(SiMe₃)₂)₃, Y(N(iPr)₂)₃, Y(N(tBu)SiMe₃)₃, Y(TMPD)₃,Cp₃Y, (MeCp)₃Y, ((nPr)Cp)₃Y, ((nBu)Cp)₃Y, Y(OCMe₂CH₂NMe₂)₃, Y(THD)₃,Y[OOCCH(C₂H₅)C₄H₉]₃, Y(C₁₁H₁₉O₂)₃CH₃(OCH₂CH₂)₃OCH₃, Y(CF₃COCHCOCF₃)₃,Y(OOCC₁₀H₇)₃, Y(OOC₁₀H₁₉)₃, and Y(O(iPr))₃.

La precursors: La(N(SiMe₃)₂)₃, La(N(iPr)₂)₃, La(N(tBu)SiMe₃)₃,La(TMPD)₃, ((iPr)Cp)₃La, Cp₃La, Cp₃La(NCCH₃)₂, La(Me₂NC₂H₄Cp)₃,La(THD)₃, La[OOCCH(C₂H₅)C₄H₉]₃, La(C₁₁H₁₉O₂)₃.CH₃(OCH₂CH₂)₃OCH₃,La(C₁₁H₁₉O₂)₃.CH₃(OCH₂CH₂)₄OCH₃, La(O(iPr))₃, La(OEt)₃, La(acac)₃,La(((tBu)₂N)₂CMe)₃, La(((iPr)₂N)₂CMe)₃, La(((tBu)₂N)₂C(tBu))₃,La(((iPr)₂N)₂C(tBu))₃, and La(FOD)₃.

Ce precursors: Ce(N(SiMe₃)₂)₃, Ce(N(iPr)₂)₃, Ce(N(tBu)SiMe₃)₃,Ce(TMPD)₃, Ce(FOD)₃, ((iPr)Cp)₃Ce, Cp₃Ce, Ce(Me₄Cp)₃, Ce(OCMe₂CH₂NMe₂)₃,Ce(THD)₃, Ce[OOCCH(C₂H₅)C₄H₉]₃, Ce(C₁₁H₁₉O₂)₃.CH₃(OCH₂CH₂)₃OCH₃,Ce(C₁₁H₁₉O₂)₃.CH₃(OCH₂CH₂)₄OCH₃, Ce(O(iPr))₃, and Ce(acac)₃.

Pr precursors: Pr(N(SiMe₃)₂)₃, ((iPr)Cp)₃Pr, Cp₃Pr, Pr(THD)₃, Pr(FOD)₃,(C₅Me₄H)₃Pr, Pr[OOCCH(C₂H₅)C₄H₉]₃, Pr(C₁₁H₁₉O₂)₃.CH₃(OCH₂CH₂)₃OCH₃,Pr(O(iPr))₃, Pr(acac)₃, Pr(hfac)₃, Pr(((tBu)₂N)₂CMe)₃,Pr(((iPr)₂N)₂CMe)₃, Pr(((tBu)₂N)₂C(tBu))₃, and Pr(((iPr)₂N)₂C(tBu))₃.

Nd precursors: Nd(N(SiMe₃)₂)₃, Nd(N(iPr)₂)₃, ((iPr)Cp)₃Nd, Cp₃Nd,(C₅Me₄H)₃Nd, Nd(THD)₃, Nd[OOCCH(C₂H₅)C₄H₉]₃, Nd(O(iPr))₃, Nd(acac)₃,Nd(hfac)₃, Nd(F₃CC(O)CHC(O)CH₃)₃, and Nd(FOD)₃.

Sm precursors: Sm(N(SiMe₃)₂)₃, ((iPr)Cp)₃Sm, Cp₃Sm, Sm(THD)₃,Sm[OOCCH(C₂H₅)C₄H₉]₃, Sm(O(iPr))₃, Sm(acac)₃, and (C₅Me₅)₂Sm.

Eu precursors: Eu(N(SiMe₃)₂)₃, ((iPr)Cp)₃Eu, Cp₃Eu, (Me₄Cp)₃Eu,Eu(THD)₃, Eu[OOCCH(C₂H₅)C₄H₉]₃, Eu(O(iPr))₃, Eu(acac)₃, and (C₅Me₅)₂Eu.

Gd precursors: Gd(N(SiMe₃)₂)₃, ((iPr)Cp)₃Gd, Cp₃Gd, Gdd(THD)₃,Gd[OOCCH(C₂H₅)C₄H₉]₃, Gd(O(iPr))₃, and Gd(acac)₃.

Tb precursors: Tb(N(SiMe₃)₂)₃, ((iPr)Cp)₃Tb, Cp₃Tb, Tb(THD)₃,Tb[OOCCH(C₂H₅)C₄H₉]₃, Tb(O(iPr))₃, and Tb(acac)₃.

Dy precursors: Dy(N(SiMe₃)₂)₃, ((iPr)CP)₃Dy, Cp₃Dy, Dy(THD)₃,Dy[OOCCH(C₂H₅)C₄H₉]₃, Dy(O(iPr))₃, Dy(O₂C(CH₂)₆CH₃)₃, and Dy(acac)₃.

Ho precursors: Ho(N(SiMe₃)₂)₃, ((iPr)Cp)₃Ho, Cp₃Ho, Ho(THD)₃,Ho[OOCCH(C₂H₅)C₄H₉]₃, Ho(O(iPr))₃, and Ho(acac)₃.

Er precursors: Er(N(SiMe₃)₂)₃, ((iPr)Cp)₃Er, ((nBu)Cp)₃Er, Cp₃Er,Er(THD)₃, Er[OOCCH(C₂H₅)C₄H₉]₃, Er(O(iPr))₃, and Er(acac)₃.

Tm precursors: Tm(N(SiMe₃)₂)₃, ((iPr)Cp)₃Tm, Cp₃Tm, Tm(THD)₃,Tm[OOCCH(C₂H₅)C₄H₉]₃, Tm(O(iPr))₃, and Tm(acac)₃.

Yb precursors: Yb(N(SiMe₃)₂)₃, Yb(N(iPr)₂)₃, ((iPr)Cp)₃Yb, Cp₃Yb,Yb(THD)₃, Yb[OOCCH(C₂H₅)C₄H₉]₃, Yb(O(iPr))₃, Yb(acac)₃, (C₅Me₅)₂Yb,Yb(hfac)₃, and Yb(FOD)₃.

Lu precursors: Lu(N(SiMe₃)₂)₃, ((iPr)Cp)₃Lu, Cp₃Lu, Lu(THD)₃,Lu[OOCCH(C₂H₅)C₄H₉]₃, Lu(O(iPr))₃, and Lu(acac)₃.

In the above precursors, as well as precursors set forth below, thefollowing common abbreviations are used: Si: silicon; Me: methyl; Et:ethyl; iPr: isopropyl; nPr: n-propyl; Bu: butyl; nBu: n-butyl; sBu:sec-butyl; iBu: iso-butyl; tBu: tert-butyl; Cp: cyclopentadienyl; THD:2,2,6,6-tetramethyl-3,5-heptanedionate; TMPD:2,2,6,6-tetramethylpiperidide; acac: acetylacetonate; hfac:hexafluoroacetylacetonate; mmp: methoxy-2-dimethyl-2-propionate; andFOD: 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate.

Embodiments of the invention may utilize a wide variety of Group IIIprecursors for incorporating aluminum into the nitride films. Forexample, many aluminum precursors have the formula:AIL¹L²L³D_(x)where L¹, L², L³ are individual anionic ligands, and D is a neutraldonor ligand where x can be 0, 1, or 2. Each L¹, L², L³ ligand may beindividually selected from the groups of alkoxides, halides, aryloxides,amides, cyclopentadienyls, alkyls, silyls, amidinates, β-diketonates,ketoiminates, silanoates, and carboxylates. D ligands may be selectedfrom groups of ethers, furans, pyridines, pyroles, pyrolidines, amines,crown ethers, glymes, and nitriles.

Other examples of Group III precursors include: Al₂Me₆, Al₂Et₆,[Al(O(sBu))₃]₄, Al(CH₃COCHCOCH₃)₃, AlBr₃, AlI₃, Al(O(iPr))₃,[Al(NMe₂)₃]₂, Al(iBu)₂Cl, Al(iBu)₃, Al(iBu)₂H, AlEt₂Cl, Et₃Al₂(O(sBu))₃,Al(THD)₃, GaCl₃, InCl₃, GaH₃, and InH₃.

Examples of silicon precursors include, but are not limited to, silane(SiH₄), disilane (Si₂H₆), monochlorosilane (SiClH₃), dichlorosilane(SiH₂Cl₂), trichlorosilane (SiHCl₃), hexachlorodisilane (Si₂Cl₆),diethylsilane, and alkylaminosilane compounds. Examples ofalkylaminosilane compounds include, but are not limited to,di-isopropylaminosilane (H₃Si(NiPr₂)), bis(diethylamino)silane(H₂Si(NEt₂)₂, bis(diisopropylamino)silane (H₂Si(NiPr₂)₂,tris(isopropylamino)silane (HSi(NiPr₂)₃), bis(tert-butylamino)silane((tBu(H)N)₂SiH₂), tetrakis(dimethylamino)silane (Si(NMe₂)₄),tetrakis(ethylmethylamino)silane (Si(NEtMe)₄),tetrakis(diethylamino)silane (Si(NEt₂)₄), tris(dimethylamino)silane(HSi(NMe₂)₃), tris(ethylmethylamino)silane (HSi(NEtMe)₃),tris(diethylamino)silane (HSi(NEt₂)₃), and tris(dimethylhydrazino)silane(HSi(N(H)NMe₂)₃).

Examples of nitrogen precursors include N₂, NH₃, N₂H₄, and C₁-C₁₀alkylhydrazine compounds. Common C₁ and C₂ alkylhydrazine compoundsinclude monomethyl-hydrazine (MeNHNH₂), 1,1-dimethyl-hydrazine(Me₂NNH₂), and 1,2-dimethyl-hydrazine (MeNHNHMe).

The present inventors have realized that exposing a substrate to a metalprecursor and one or more nitrogen precursors having differentreactivity characteristics toward the metal precursor can be utilized todeposit a strained metal nitride film on the substrate. Thus, a strainedmetal nitride film can be formed as the metal nitride film is deposited,rather than by the conventional method of post processing of depositedfilms. Thus, embodiments of the present invention may reduce productiontime and equipment necessary for forming a strained metal nitride film.Further, the strain provided during deposition of the metal nitride filmmay be better controlled than that of post processing methods. Forexample, a predetermined strain gradient throughout the metal nitridefilm (rather than in only a surface region) can be provided by aparticular process recipe for forming the strained metal nitride film.In particular, processing conditions such as the type of precursorsused, the relative amounts of precursors used and/or exposure time toeach precursor can be set to provide a predetermined strain in the metalnitride film. Further, embodiments of the invention may also providebetter control of thickness and conformality of the metal nitride filmthan methods currently in practice.

FIGS. 3A-3E and FIGS. 4A-4E, are process flow diagrams for formingstrained metal nitride according to embodiments of the invention. FIGS.6A-6E and FIGS. 7A-7E, are process flow diagrams for forming strainedmetal silicon nitride according to embodiments of the invention. Themetal precursors, silicon precursors, and nitrogen precursors describedabove may be utilized to form these films.

FIG. 3A is a process flow diagram for forming a strained metal nitridefilm on a substrate in a process chamber according to an embodiment ofthe invention. The process 300 of FIG. 3A may, for example, be performedto form a CMOS structure such as that shown in of FIG. 1. The process300 may be performed in processing system 1 of FIG. 2A, for example. InFIG. 3A, the process 300 includes, in step 302, exposing a substrate toa gas containing a metal precursor and optionally an inert gas such asAr.

In step 304, the substrate is exposed to a gas containing a firstnitrogen precursor configured to react with the metal precursor with afirst reactivity characteristic. For example, the first nitrogenprecursor may react with the metal precursor within a processing spaceof the chamber, or with the metal precursor adsorbed on a surface of thesubstrate, or both.

In step 306, the substrate is exposed to a gas containing a secondnitrogen precursor configured to react with the metal precursor with asecond reactivity characteristic different than the first reactivitycharacteristic. In the process 300, the term reactivity characteristicrefers to any characteristic of the reaction between a nitrogenprecursor and a metal precursor that affects a property of a metalnitride film formed on the substrate. For example, as noted above,different reactivity characteristics may be expected based on differentheat of formation (ΔH) for the first and second nitrogen precursors, andtherefore different heat of formation for deposition of the metalnitride film. A property affected by a reactivity characteristic can bedensity of the metal nitride film. According to one embodiment, thefirst and second nitrogen precursors can be different precursormaterials. For example, the first and second nitrogen precursors areselected from NH₃ and N₂H₄. However, the first and second precursors maybe the same mixture of materials in different mixture ratios, as will bediscussed below. In steps 304 and 306, the gas containing the first andsecond nitrogen precursors may further contain an inert gas such as Ar.

The steps of the process 300 depicted in FIG. 3A can be continued for apredetermined time or repeated a predetermined number of times until astrained metal nitride film with a desired thickness has been depositedonto the substrate. Further, the sequence of steps 302, 304 and 306 ofthe process 300 can vary widely in accordance with embodiments of theinvention. For example, the metal precursor, the first nitrogenprecursor, and the second nitrogen precursor can be provided in aprocess chamber as discrete pulses having no temporal overlap (e.g., anALD process). Alternatively, the metal precursor, the first nitrogenprecursor, and the second nitrogen precursor can be providedsimultaneously (e.g., a CVD process) while varying a ratio or the firstand second nitrogen precursors. Some combination of these methods mayalso be used. For example, the metal precursor can be continuouslyprovided to the process chamber while the first and second nitrogenprecursors are pulsed, or both the metal precursor and first nitrogenprecursors can be continuously provided, while the second nitrogenprecursor is pulsed. As would be understood by one of ordinary skill inthe art, various combinations are possible, and embodiments of theinvention are not limited by the specific examples described in FIGS.3A-3E herein.

FIG. 3B is a process flow diagram for forming a strained metal nitridefilm according to an embodiment of the invention. The process 320depicted in FIG. 3B is an ALD process that includes sequential gasexposures of a metal precursor and nitrogen precursors with partial orno temporal overlap between the different gas pulses. The process 320includes, in step 322, exposing a substrate to a gas pulse containing ametal precursor and optionally an inert gas such as Ar.

In step 324, the substrate is exposed to a gas pulse containing a firstnitrogen precursor or a gas pulse containing the first nitrogenprecursor and a second nitrogen precursor in a first ratio. The firstratio may, for example, be defined as N₁/N₂ or N₁/(N₁+N₂), where N₁ andN₂ refer to the amounts of the first and second nitrogen precursors,respectively. According to one embodiment, the first ratio may be variedfrom a ratio corresponding to substantially pure first nitrogenprecursor, to another ratio corresponding to a combination of the firstand second nitrogen precursors, to yet another ratio corresponding tosubstantially pure second nitrogen precursor. In one example, a ratioN₁/(N₁+N₂) may increase monotonically as 0, 0.05, 0.10, . . . , 0.90,0.95, and 1.0, during deposition of the metal nitride film. The firstand second nitrogen precursors can, for example, be selected from NH₃,N₂H₄, and C₁-C₁₀ alkylhydrazine compounds. According to one embodiment,the first and second nitrogen precursors are selected from NH₃ and N₂H₄.The gas, pulse may further contain an inert gas such as Ar.

In step 326, the substrate is exposed to a second gas pulse containingthe metal precursor and optionally an inert gas such as Ar. In step 328,the substrate is exposed to a gas pulse containing the second nitrogenprecursor or a gas pulse containing the first nitrogen precursor and thesecond nitrogen precursor in a second ratio different from the firstratio. Thus, in the embodiment of FIG. 3B, first and second nitrogenprecursors, and first and second ratios of different nitrogen precursorsare explicitly described. However, as noted above, the first and secondprecursors may be considered the same mixture of materials in differentmixture ratios. The gas pulse can further contain an inert gas such asAr.

The steps 322-328 may be repeated a predetermined number of times asshown by the process flow 334 until a strained metal nitride film with adesired thickness has been deposited onto the substrate. The processchamber may be purged with an inert gas, evacuated, or both purged andevacuated after each of steps 322, 324, 326, and 328.

According to one embodiment, steps 322 and 324 may be sequentiallyperformed a first number of times as shown by the process flow 330,prior to performing steps 326 and 328.

According to another embodiment, steps 326 and 328 may be sequentiallyperformed a second number of times as shown by the process flow 332,prior to repeating steps 322 and 324 in the process flow 334. In thisregard, it is to be understood that the terms “a first number of times”and “a second number of times” are used to provide different terms forease of understanding. However, the first and second number of times canbe the same or a different number.

According to yet another embodiment, steps 322 and 324 may besequentially performed a first number of times prior to performing steps326 and 328 as shown by the process flow 330, and steps 326 and 328 maybe sequentially performed a second number of times as shown by theprocess flow 332, prior to repeating steps 322 and 324 in the processflow 334.

According to one embodiment, step 324 comprises exposing the substrateto a gas pulse containing a first nitrogen precursor and step 328comprises exposing the substrate to a gas pulse containing a secondnitrogen precursor. Furthermore, steps 322 and 324 may be sequentiallyperformed a first number of times as shown by the process flow 330,prior to performing steps 326 and 328. Furthermore, steps 326 and 328may be sequentially performed a second number of times as shown by theprocess flow 332, prior to repeating steps 322 and 324 in the processflow 334.

According to one embodiment, steps 322 and 324 may be sequentiallyperformed a first number of times that decreases monotonically and steps326 and 328 may be sequentially performed a second number of times thatincreases monotonically each time process flow 334 is performed. In oneexample, in step 322, the substrate is exposed to a gas pulse containinga metal precursor, in step 324, the substrate is exposed to a gas pulsecontaining a first nitrogen precursor, and steps 322 and 324 arerepeating twice using the process flow 330. Thereafter, in step 326, thesubstrate is exposed to a gas pulse containing the metal precursor, andin step 328; the substrate is exposed to a gas pulse containing a secondnitrogen precursor. Next, in step 322, the substrate is exposed to a gaspulse containing the precursor, in step 324, the substrate is exposed toa gas pulse containing the first nitrogen precursor, and steps 322 and324 are repeated once using the process flow 330. Thereafter, in step326, the substrate is exposed to a gas pulse containing the metalprecursor, in step 328, the substrate is exposed to a gas pulsecontaining the second nitrogen precursor, and steps 326 and 328 arerepeated once using the process flow 332. Next, in step 322, thesubstrate is exposed to a gas pulse containing the metal precursor, andin step 324, the substrate is exposed to a gas pulse containing thefirst nitrogen precursor without repeat using process flow 330.Thereafter, in step 326, the substrate is exposed to a gas pulsecontaining the metal precursor, in step 328, the substrate is exposed toa gas pulse containing the second nitrogen precursor, and steps 326 and328 are repeated twice using process flow 332. In this example, thefirst number of times decreases from 3 to 2 to 1 and the second numberof times increases from 1 to 2 to 3 during deposition of the strainedmetal nitride film. In one example, the first and second nitrogenprecursors can be selected from NH₃and N₂H₄.

According to one embodiment of the invention, steps 322) and 324) ofFIG. 3B may have at least partial temporal overlap. According to anotherembodiment of the invention, steps 326) and 328) may have at leastpartial temporal overlap. According to yet another embodiment of theinvention, steps 326 and 328 may have no temporal overlap and steps 326and 328 may have no temporal overlap.

FIG. 3C is a process flow diagram for forming a strained metal nitridefilm according to another embodiment of the present invention. Theprocess 340 includes, in step 342, selecting a ratio of first and secondnitrogen precursors. The ratio can range from a first nitrogen precursoronly, to a mixture of the first and second nitrogen precursor, to thesecond nitrogen precursor only. In step 344, the substrate is exposed toa gas pulse containing a metal precursor, and in step 346, the substrateis exposed to a gas pulse containing the first and second nitrogenprecursors in the selected ratio. In step 348, the ratio is adjusted andstep 344 is repeated as shown by the process flow 350. According to oneembodiment, the ratio of the first and second nitrogen precursors canmonotonically increase or decrease during deposition of the metalnitride film. The process 340 may be performed as a pulsed CVD processthat includes interrupted gas exposures of a metal precursor anddifferent nitrogen precursors with at least partial temporal overlap ofthe gas pulses in steps 344 and 346. Alternately, the process 340 may beperformed as an ALD process with no overlap of the gas pulses in steps344 and 346.

FIG. 3D is a process flow diagram for forming a strained metal nitridefilm according to another embodiment of the present invention. Theprocess 360 includes, in step 362, exposing a substrate to a gas pulsecontaining a metal precursor and a first nitrogen precursor or a gaspulse containing the metal precursor, the first nitrogen precursor, anda second nitrogen precursor, where the gas pulse contains the first andsecond nitrogen precursors in a first ratio. In step 364, the substrateis exposed to a gas pulse containing the metal precursor and the secondnitrogen precursor, or a gas pulse containing the metal precursor andthe first and second nitrogen precursors in a second ratio. Steps 362and 364 can be repeated to deposit the metal nitride film to a desiredthickness as shown by process flow 366. According to one embodiment, thefirst ratio can monotonically increase and the second ratio canmonotonically decrease during deposition of the metal nitride film.

FIG. 3E is a process flow diagram for forming a strained metal nitridefilm according to another embodiment of the present invention. Theprocess 380 includes, in step 382, exposing a substrate to a gascontaining a metal precursor and first and second nitrogen precursors,where a ratio of the first and second nitrogen precursors is variedduring the exposure. In one example the ratio of the first and secondnitrogen precursors can monotonically increase or decrease duringdeposition of the metal nitride film.

FIG. 4A is a process flow diagram for forming a strained metal nitridefilm on a substrate in a process chamber according to an embodiment ofthe present invention. The process 400 of FIG. 4A may be performed in aprocessing system 2 of FIG. 2B, for example. As seen in FIG. 4A, theprocess 400 includes, in step 402, exposing a substrate to a gascontaining a metal precursor and optionally an inert gas such as Ar.

In step 404, the substrate is exposed to a gas containing a nitrogenprecursor activated by a plasma source at a first level of plasma powerto react with the metal precursor with a first reactivitycharacteristic. In one embodiment, the first level of plasma power isless than a plasma activation power (e.g., 0 W) and therefore a plasmais not activated. The plasma activation of the nitrogen precursoraffects a property of a metal nitride film formed on the substrate, forexample the deposition rate and the density of the metal nitride film.The plasma activated nitrogen precursor may react with the metalprecursor within a processing space of the chamber, or with metalprecursor adsorbed on a surface of the substrate, or both.

In step 406, the substrate is exposed to a gas containing the nitrogenprecursor activated by the plasma source at a second level of plasmapower to react with the metal precursor with a second reactivitycharacteristic different than the first reactivity characteristic.

Plasma activation of a nitrogen precursor (or other precursors) canresult in electronic excitation and/or ionization of the nitrogenprecursor that affects reactivity towards a metal precursor. Inaddition, plasma activation can result in at least partial dissociationof the nitrogen precursor, thereby creating a modified nitrogenprecursor with a different reactivity towards the metal precursor.Increasing the level of plasma power and plasma density, for example,will generally increase the amount of electronically excited, ionized,and at least partially dissociated nitrogen precursor. In addition,increased levels of plasma power and plasma density may be utilized tovary the concentration of additional charged species (e.g., Argon ions,electrons, or both) in the plasma environment. These additional chargedspecies may interact with the metal nitride film and the substrateduring deposition, thereby affecting a reactivity characteristic and aproperty (e.g., density, strain) of at least a portion of a thickness ofthe metal nitride film.

The steps of the process 400 depicted in FIG. 4A can be continued for apredetermined time or repeated a predetermined number of times until astrained metal nitride film with a desired thickness has been depositedonto the substrate. Further, the sequence of steps 402, 404 and 406 ofthe process 400 can vary widely in accordance with embodiments of theinvention. For example, the metal precursor and the plasma activatednitrogen precursor can be provided in the process chamber as discretegas pulses having no temporal overlap, where the level of plasma poweris varied for the discrete gas pulses. Alternatively, the metalprecursor and the nitrogen precursor may be flowed continuously whilesimply varying the level of plasma power. Some combination of thesemethods may also be used. For example, the metal precursor can becontinuously provided to the chamber while the nitrogen precursor andthe plasma are pulsed at different levels of plasma power, or both themetal and the nitrogen precursor can be continuously provided and theplasma is pulsed at different levels of plasma power. As would beunderstood by one of ordinary skill in the art, various combinations arepossible, and embodiments of the invention are not limited by thespecific examples described in FIGS. 4A-4E herein.

FIG. 4B is a process flow diagram for forming a strained metal nitridefilm according to an embodiment of the invention. The process 420 is aPEALD process similar to the ALD process 320 of FIG. 3B and includessequential gas exposures of a metal precursor and a plasma activatednitrogen precursor with partial or no temporal overlap between thedifferent gas pulses.

The process 420 includes, in step 422, exposing a substrate to a gaspulse containing a metal precursor and optionally an inert gas such asAr. In step 424, the substrate is exposed to a gas pulse containing anitrogen precursor activated by a plasma source at a first level ofplasma power. In step 426, the substrate is exposed to a second gaspulse containing the metal precursor. In step 428, the substrate isexposed to a gas pulse containing the nitrogen precursor activated bythe plasma source at a second level of plasma power.

FIGS. 5A and 5B show power graphs depicting different levels of plasmapower coupled to a process chamber in accordance with embodiments of theinvention. As shown by the exemplary power curve 510 in FIG. 5A, thelevel of plasma power may be applied to the process chamber in aplurality discrete levels, 520, 530, and 540. In one example, the powerlevel 520 may be at or below a lower limit for plasma formation and thepower level 540 may correspond to a maximum desired level of plasmapower. The maximum desired level of plasma power is preferably nothigher than a level determined to disrupt or damage the substrateincluding any deposited films thereon. As seen in FIG. 5B, the level ofplasma power may be applied to the process chamber in a continuouslychanging fashion represented by the power curve 550.

As would be understood by one of ordinary skill in the art, the powercurves of FIGS. 5A and 5B are exemplary, and the varying level of plasmapower may depend on the composition and characteristic of the film to bedeposited by the process. For example, the plasma power of FIG. 5A caninclude more than three (3) discrete levels of plasma power, and theplasma power of FIG. 5B may change in a non-linear fashion. Moreover, acombination of stepped and ramped power can be used to vary the level ofplasma power. Further, the power may be provided in discrete pulseswhere power is on or off. Still further, suitable high levels of plasmapower that enable deposition of a film at improved deposition speeds andwith reduced impurities in accordance with an embodiment of theinvention can be determined by direct experimentation and/or design ofexperiments (DOE). Other adjustable process parameters such as substratetemperature, process pressure, type of process gas and relative gasflows can also be determined by direct experimentation and/or DOE.

Referring back to FIG. 4A, steps 422-428 may be repeated a predeterminednumber of times as shown by the process flow 434 until a strained metalnitride film with a desired thickness has been deposited onto thesubstrate. The process chamber may be purged with an inert gas,evacuated, or both purged and evacuated after each of steps 422, 424,426, and 428.

According to one embodiment, steps 422 and 424 may be sequentiallyperformed a first number of times as shown by the process flow 430,prior to performing steps 426 and 428.

According to another embodiment, steps 426 and 428 may be sequentiallyperformed a second number of times as shown by the process flow 432,prior to repeating steps 422 and 424 in the process flow 434.

According to yet another embodiment, steps 422 and 424 may besequentially performed a first number of times prior to performing steps426 and 428 as shown by the process flow 430, and steps 426 and 428 maybe sequentially performed a second number of times as shown by theprocess flow 432, prior to repeating steps 422 and 424 in the processflow 434.

According to one embodiment, the first number of times may decreasemonotonically and the second number of times may increase monotonicallyeach time process flow 434 is performed. In one example, in step 422,the substrate is exposed to a gas pulse containing a metal precursor, instep 424, the substrate is exposed to a gas pulse containing a nitrogenprecursor activated by a plasma source at a first level of plasma power,and steps 422 and 424 are repeated twice using the process flow 430.Thereafter, in step 426, the substrate is exposed to a gas pulsecontaining the metal precursor, and in step 428, the substrate isexposed to a gas pulse containing the nitrogen precursor activated bythe plasma source at a second level of plasma power. Next, in step 422,the substrate is exposed to a gas pulse containing the precursor, instep 424, the substrate is exposed to a gas pulse containing thenitrogen precursor activated by the plasma source at the first level ofplasma power, and steps 422 and 424 are repeated once using the processflow 430. Thereafter, in step 426, the substrate is exposed to a gaspulse containing the metal precursor, in step 428, the substrate isexposed to a gas pulse containing the nitrogen precursor activated bythe plasma source at a first level of plasma power, and steps 426 and428 are repeated once using the process flow 432. Next, in step 422, thesubstrate is exposed to a gas pulse containing the metal precursor, andin step 424, the substrate is exposed to a gas pulse containing thenitrogen precursor activated by the plasma source at the first level ofplasma power. Thereafter, in step 426, the substrate is exposed to a gaspulse containing the metal precursor, in step 428, the substrate isexposed toga gas pulse containing the nitrogen precursor activated bythe plasma source at the second level of plasma power, and steps 426 and428 are repeated twice using process flow 432. In this example, thefirst number of times decreases from 3 to 2 to 1 and the second numberof times increases from 1 to 2 to 3 during deposition of the strainedmetal nitride film. In one example, the nitrogen precursor can beselected from NH₃ and N₂H₄.

Still referring to FIG. 4B, according to one embodiment of theinvention, the gas pulse in step 424 may further comprise a dilution gasin a first ratio with the nitrogen precursor, and step 428 may furthercomprise the dilution gas in a second ratio with the nitrogen precursor,where the second ratio is different from the first ratio. The additionof a dilution gas to a nitrogen precursor can affect the plasma densityin the process chamber and thus the amount of activated nitrogenprecursor available to interact with the metal precursor. The dilutiongas may be selected from He, Ar, Ne, Kr, Xe, H₂, or N₂, or a combinationof two or more thereof. The first ratio may, for example, be defined asD/N or D/(D+N), where D and N refer to the amounts of the dilution gasand the nitrogen precursor, respectively. According to one embodiment,the first ratio may be varied from ratio corresponding to substantiallypure nitrogen precursor, to a another ratio corresponding to acombination of the dilution gas and the nitrogen precursor, to yetanother ratio corresponding to substantially pure dilution gas. In oneexample, a ratio D/(D+N) may increase monotonically as 0, 0.05, 0.10, .. . , 0.90, 0.95, and 1.0, during deposition of the metal nitride film.

FIG. 4C is a process flow diagram for forming a strained metal nitridefilm according to another embodiment of the present invention. Theprocess 440 includes, in step 442, selecting a level of plasma power.The level of plasma power can range from a first level at or below alower limit for plasma formation to a second level of plasma powercorresponding to a maximum desired level of plasma power. Thus, thefirst level of plasma power can be 0 W of plasma power. In step 444, thesubstrate is exposed to a gas pulse, containing a metal precursor, andin step 446, the substrate is exposed to a gas pulse containing anitrogen precursor activated by the plasma source at the selected levelof plasma power. In step 448, the level of plasma power is adjusted, andstep 444 is repeated as shown by the process flow 450. According to oneembodiment, the level of plasma power can monotonically increase ordecrease during deposition of the metal nitride film. The process 440may be performed as a pulsed PECVD process that includes interrupted gasexposures of a metal precursor and a plasma activated nitrogen precursorwith at least partial temporal overlap of the gas pulses in steps 444and 446. Alternately, the process 440 may be performed as a PEALDprocess with no overlap of the gas pulses in steps 444 and 446.

Still referring to FIG. 4C, according to one embodiment of theinvention, the gas pulse in step 446 may further comprise a dilution gasin a first ratio with the nitrogen precursor, and step 448 may furthercomprise adjusting the amount of dilution gas from the first ratio to asecond ratio different from the first ratio.

FIG. 4D is a process flow diagram for forming a strained metal nitridefilm according to another embodiment of the invention. The process 460includes, in step 462, exposing a substrate to a gas pulse containing ametal precursor and a nitrogen precursor activated by a plasma source ata first level of plasma power. In step 464, the substrate is exposed toa gas pulse containing the metal precursor and the nitrogen precursoractivated by the plasma source at a second level of plasma powerdifferent from the first level of plasma power. According to oneembodiment of the invention, the gas pulse in step 462 may furthercomprise a dilution gas in a first ratio with the nitrogen precursor andstep 464 may further comprises the dilution gas in a second ratio withthe nitrogen precursor, where the second ratio is different from thefirst ratio.

FIG. 4E is a process flow diagram for forming a strained metal nitridefilm according to another embodiment of the present invention. Theprocess 480 includes, in step 482, exposing a substrate to a gascontaining a metal precursor and a nitrogen precursor activated by aplasma source at a level of plasma power that is varied during theexposure. In one example the level of plasma power can monotonicallyincrease or decrease during deposition of the metal nitride film.According to one embodiment of the invention, the gas pulse in step 482may further comprise a dilution gas in a ratio with the nitrogenprecursor where the ratio is varied during the exposure. In one examplethe ratio can monotonically increase or decrease during deposition ofthe metal nitride film.

The present inventors have realized that exposing a substrate to a metalprecursor, a silicon precursor, and one or more nitrogen precursorshaving different reactivity characteristics toward the metal precursoror the silicon precursor can be utilized to deposit a strained metalsilicon nitride film on the substrate. Thus, a strained metal siliconnitride film can be formed as the metal silicon nitride film isdeposited, rather than by the conventional method of post processing ofdeposited films. Thus, embodiments of the present invention may reduceproduction time and equipment necessary for forming a strained metalsilicon nitride film. Further, the strain provided during deposition ofthe metal silicon nitride film may be better controlled than that ofpost processing methods. For example, a predetermined strain gradientthroughout the metal silicon nitride film (rather than in only a surfaceregion) can be provided by a particular process recipe for forming thestrained metal silicon nitride film. In particular, processingconditions such as the type of precursors used, the relative amounts ofprecursors used, exposure time to each precursor can be set to provide apredetermined strain in the metal silicon nitride film. Further,embodiments of the invention may also provide better control ofthickness and conformality of the metal silicon nitride film thanmethods currently in practice.

The processes of FIGS. 3A-3E and FIGS. 4A-4E may further includeactivating a plasma during one or more of the exposing steps. Further, apower coupled to the plasma may be varied to provide a differentreactivity characteristic, as will be discussed below. That is, theembodiments of FIGS. 3A-3E and FIGS. 4A-4E using different first andsecond nitrogen precursors (or different ratios of first and secondnitrogen precursors) may be combined with the plasma power variationembodiments discussed below.

FIG. 6A is a process flow diagram for forming a strained metal siliconnitride film on a substrate in a process chamber according to anembodiment of the invention. The process 600 of FIG. 6A may, forexample, be performed to form a CMOS structure such as that shown in ofFIG. 1. The process 600 may be performed in processing system 1 of FIG.2A, for example. As seen in FIG. 6A, the process 600 includes, in step602, exposing a substrate to a gas containing a metal precursor andoptionally an inert gas such as Ar. In step 604, the substrate isexposed to a gas containing a silicon precursor and optionally an inertgas such as Ar.

In step 606, the substrate is exposed to a gas containing a firstnitrogen precursor configured to react with the metal precursor or thesilicon precursor with a first reactivity characteristic. For example,the first nitrogen precursor may react with metal precursor or thesilicon precursor within a processing space of the chamber, or with themetal precursor or the silicon precursor adsorbed on a surface of thesubstrate, or both.

In step 608, the substrate is exposed to a gas containing a secondnitrogen precursor configured to react with the metal precursor or thesilicon precursor with a second reactivity characteristic different thanthe first reactivity characteristic. In the process of 608, the termreactivity characteristic refers to any characteristic of the reactionbetween a nitrogen precursor and a metal precursor or a siliconprecursor that affects a property of a metal silicon nitride film formedon the substrate. For example, as noted above, different reactivitycharacteristics may be expected based on different heat of formation(ΔH) for the first and second nitrogen precursors, and thereforedifferent heat of formation for deposition of the metal silicon nitridefilm. A property affected by a reactivity characteristic can be densityof the metal silicon nitride film. According to one embodiment, thefirst and second nitrogen precursors are selected from NH₃ and N₂H₄. Insteps 606 and 608, the gas containing the first and second nitrogenprecursors may further contain an inert gas such as Ar.

The steps of the process 600 depicted in FIG. 6A can be continued for apredetermined time or repeated a predetermined number of times until astrained metal silicon nitride film with a desired thickness has beendeposited onto the substrate. Further, the sequence of steps 602, 604,606, and 608 of the process 600 can vary widely in accordance withembodiments of the invention. For example, the metal precursor, thesilicon precursor, the first nitrogen precursor, and the second nitrogenprecursor can be provided in a process chamber as discrete pulses havingno temporal overlap (e.g., an ALD process). Alternatively, the metalprecursor, silicon precursor, the first nitrogen precursor, and thesecond nitrogen precursor can be provided simultaneously (e.g., a CVDprocess) while varying a ratio or the first and second nitrogenprecursors. Some combination of these methods may also be used. Forexample, the metal precursor and the silicon precursor can becontinuously provided to the process chamber while the first and secondnitrogen precursors are pulsed, or the metal precursor, the siliconprecursor, and the first nitrogen precursor can be continuouslyprovided, while the second nitrogen precursor is pulsed. As would beunderstood by one of ordinary skill in the art, various combinations arepossible, and embodiments of the invention are not limited by thespecific examples described in FIGS. 6A-6E herein.

FIG. 6B is a process flow diagram for forming a strained metal siliconnitride film according to an embodiment of the invention. The process620 depicted in FIG. 6B is an ALD process that includes sequential gasexposures of a metal precursor, a silicon precursor, and nitrogenprecursors with partial or no temporal overlap between the different gaspulses. The process 620 includes, in step 622, exposing a substrate to agas pulse containing a metal precursor and optionally an inert gas suchas Ar.

In step 624, the substrate is exposed to a gas pulse containing a firstnitrogen precursor or a gas pulse containing the first nitrogenprecursor and a second nitrogen precursor in a first ratio. The firstratio may, for example, be defined as N₁/N₂ or N₁/(N₁+N₂), where N₁ andN₂ refer to the amounts of the first and second nitrogen precursors,respectively. According to one embodiment, the first ratio may be variedfrom a ratio corresponding to substantially pure first nitrogenprecursor, to another ratio corresponding to a combination of the firstand second nitrogen precursors, to yet another ratio corresponding tosubstantially pure second nitrogen precursor. In one example, a ratioN₁/(N₁+N₂) may increase monotonically as 0, 0.05, 0.10, . . . , 0.90,0.95, and 1.0, during deposition of the metal silicon nitride film. Thefirst and second nitrogen precursors can, for example, be selected fromNH₃, N₂H₄, and C₁-C₁₀ alkylhydrazine compounds. According to oneembodiment, the first and second nitrogen precursors are selected fromNH₃ and N₂H₄. The gas pulse may further contain an inert gas such as Ar.

In step 626, the substrate is exposed to a gas pulse containing asilicon precursor and optionally an inert gas such as Ar. In step 628,the substrate is exposed to a gas pulse containing the second nitrogenprecursor or a gas pulse containing the first nitrogen precursor and thesecond nitrogen precursor in a second ratio different from the firstratio. The gas pulse can further contain an inert gas such as Ar.

The steps 622-628 may be repeated a predetermined number of times asshown by the process flow 634 until a strained metal silicon nitridefilm with a desired thickness has been deposited onto the substrate. Theprocess chamber may be purged with an inert gas, evacuated, or bothpurged and evacuated after each of steps 622, 624, 626, and 628.

According to one embodiment, steps 622 and 624 may be sequentiallyperformed a first number of times as shown by the process flow 630,prior to performing steps 626 and 628.

According to another embodiment, steps 626 and 628 may be sequentiallyperformed a second number of times as shown by the process flow 632,prior to repeating steps 622 and 624 in the process flow 634.

According to yet another embodiment, steps 622 and 624 may besequentially performed a first number of times prior to performing steps626 and 628 as shown by the process flow 630, and steps 626 and 628 maybe sequentially performed a second number of times as shown by theprocess flow 632, prior to repeating steps 622 and 624 in the processflow 634.

According to one embodiment, step 624 comprises exposing the substrateto a gas pulse containing a first nitrogen precursor and step 628comprises exposing the substrate to a gas pulse containing a secondnitrogen precursor. Furthermore, steps 622 and 624 may be sequentiallyperformed a first number of times as shown by the process flow 630,prior to performing steps 626 and 628. Furthermore, steps 626 and 628may be sequentially performed a second number of times as shown by theprocess flow 632, prior to repeating steps 622 and 624 in the processflow 634.

According to one embodiment, steps 622 and 624 may be sequentiallyperformed a first number of times that decreases monotonically and steps626 and 628 may be sequentially performed a second number of times thatincreases monotonically each time process flow 634 is performed. In oneexample, in step 622, the substrate is exposed to a gas pulse containinga metal precursor, in step 624, the substrate is exposed to a gas pulsecontaining a first nitrogen precursor, and steps 622 and 624 arerepeated twice using the process flow 630. Thereafter, in step 626, thesubstrate is exposed to a gas pulse containing a silicon precursor, andin step 628, the substrate is exposed to a gas pulse containing a secondnitrogen precursor. Next, in step 622, the substrate is exposed to a gaspulse containing the precursor, in step 624, the substrate is exposed toa gas pulse containing the first nitrogen precursor, and steps 622 and624 are repeated once using the process flow 630. Thereafter, in step626, the substrate is exposed to a gas pulse containing the siliconprecursor, in step 628, the substrate is exposed to a gas pulsecontaining the second nitrogen precursor, and steps 626 and 628 arerepeated once using the process flow 632. Next, in step 622, thesubstrate is exposed to a gas pulse containing the metal precursor, andin step 624, the substrate is exposed to a gas pulse containing thefirst nitrogen precursor without repeat using process flow 630.Thereafter, in step 626, the substrate is exposed to a gas pulsecontaining the silicon precursor, in step 628, the substrate is exposedto a gas pulse containing the second nitrogen precursor, and steps 626and 628 are repeated twice using process flow 632. In this example, thefirst number of times decreases from 3 to 2 to 1 and the second numberof times increases from 1 to 2 to 3 during deposition of the strainedmetal silicon nitride film. In one example, the first and secondnitrogen precursors can be selected from NH₃ and N₂H₄.

According to one embodiment of the invention, steps 622 and 624 of FIG.6B may have at least partial temporal overlap. According to anotherembodiment of the invention, steps 626 and 628 may have at least partialtemporal overlap. According to yet another embodiment of the invention,steps 622 and 624 may have no temporal overlap and steps 626 and 628 mayhave no temporal overlap.

FIG. 6C is a process flow diagram for forming a strained metal siliconnitride film according to another embodiment of the present invention.The process 640 includes, in step 642, selecting a ratio of first andsecond nitrogen precursors. The ratio can range from a first nitrogenprecursor only, to a mixture of the first and second nitrogenprecursors, to the second nitrogen precursor only. In step 644, thesubstrate is exposed to a gas pulse containing a metal precursor, instep 646, the substrate is exposed to a gas pulse containing a siliconprecursor, and in step 648, the substrate is exposed to a gas pulsecontaining the first and second nitrogen precursors in the selectedratio. In step 650, the ratio is adjusted and step 644 is repeated asshown by the process flow 652. According to one embodiment, the ratio ofthe first and second nitrogen precursors can monotonically increase ordecrease during deposition of the metal silicon nitride film. Theprocess 640 may be performed as a pulsed CVD process that includesinterrupted gas exposures of a metal precursor, a silicon precursor, anddifferent nitrogen precursors with at least partial temporal overlap ofthe gas pulses in steps 644, 646, and 648. Alternately, the process 640may be performed as an ALD process with no overlap of the gas pulses insteps 644, 646, and 648.

FIG. 6D is a process flow diagram for forming a strained metal siliconnitride film according to another embodiment of the present invention.The process 660 includes, in step 662, exposing a substrate to a gaspulse containing a metal precursor and a first nitrogen precursor or agas pulse containing the metal precursor, the first nitrogen precursor,and a second nitrogen precursor where the gas pulse contains the firstand second nitrogen precursors in a first ratio. In step 664, thesubstrate is exposed to a gas pulse containing a silicon precursor andthe second nitrogen precursor, or a gas pulse containing the siliconprecursor and the first and second nitrogen precursors in a secondratio. Steps 662 and 664 can be repeated to deposit the metal nitridefilm to a desired thickness as shown by process flow 366. According toone embodiment, the first ratio can monotonically increase and thesecond ratio can monotonically decrease during deposition of the metalsilicon nitride film.

According to one embodiment of the invention, the gas pulse in step 662may further contain a silicon precursor and the gas pulse in step 664may further contain a metal precursor.

According to one embodiment of the invention, in the process 660, thefirst ratio, the second ratio, or both the first and second ratios, maybe varied between a ratio corresponding to substantially pure firstnitrogen precursor and a ratio corresponding to substantially puresecond nitrogen precursor. In one example, the first or second ratiosmay be varied monotonically.

FIG. 6E is a process flow diagram for forming a strained metal siliconnitride film according to another embodiment of the present invention.The process 680 includes, in step 682, exposing a substrate to a gascontaining a metal precursor, a silicon precursor and first and secondnitrogen precursors, where a ratio of the first and second nitrogenprecursors is varied during the exposure. In one example the ratio ofthe first and second nitrogen precursors can monotonically increase ordecrease during deposition of the metal silicon nitride film.

FIG. 7A is a process flow diagram for forming a strained metal siliconnitride film on a substrate in a process chamber according to anembodiment of the present invention. The process 700 of FIG. 7A may beperformed in a processing system 2 of FIG. 2B, for example. As seen inFIG. 7A, the process 700 includes, in step 702, exposing a substrate toa gas containing a metal precursor and optionally an inert gas such asAr. In step 704, the substrate is exposed to a gas containing a siliconprecursor and optionally an inert gas such as Ar.

In step 706, the substrate is exposed to a gas containing a nitrogenprecursor activated by a plasma source at a first level of plasma powerto react with the metal precursor or the silicon precursor with a firstreactivity characteristic. In one embodiment, the first level of plasmapower is less than a plasma activation power (e.g. 0 W) and therefore aplasma is not activated. The plasma activation of the nitrogen precursoraffects a property of a metal silicon nitride film formed on thesubstrate, for example the deposition rate and the density of the metalsilicon nitride film. The plasma activated nitrogen precursor may reactwith the metal precursor or the silicon precursor within a processingspace of the chamber, or with the metal precursor or the siliconprecursor adsorbed on a surface of the substrate, or both.

In step 708, the substrate is exposed to a gas containing the nitrogenprecursor activated by the plasma source at a second level of plasmapower to react with the metal precursor or the silicon precursor with asecond reactivity characteristic different than the first reactivitycharacteristic.

The steps of the process 700 depicted in FIG. 7A can be continued for apredetermined time or repeated a predetermined number of times until astrained metal silicon nitride film with a desired thickness has beendeposited onto the substrate. Further, the sequence of steps 702, 704,706 and 708 of the process 700 can vary widely in accordance withembodiments of the invention. For example, the metal precursor, thesilicon precursor, and the nitrogen precursor can be provided in theprocess chamber as discrete gas pulses having no temporal overlap, wherethe level of plasma power is varied for the discrete gas pulses.Alternatively, the metal precursor, the silicon precursor and thenitrogen precursor may be flowed continuously while simply varying thelevel of plasma power. Some combination of these methods may also beused. For example, the metal precursor and the silicon precursor can becontinuously provided to the chamber while the nitrogen precursor andthe plasma are pulsed at different levels of plasma power, or the metal,the silicon precursor and the nitrogen precursor can be continuouslyprovided and the plasma is pulsed at different levels of plasma power.As would be understood by one of ordinary skill in the art, variouscombinations are possible, and embodiments of the invention are notlimited by the specific examples described in FIGS. 7A-7E herein.

FIG. 7B is a process flow diagram for forming a strained metal siliconnitride film according to an embodiment of the invention. The process720 is PEALD process similar to the ALD process 620 of FIG. 6B andincludes sequential gas exposures of a metal precursor, a siliconprecursor, and a plasma activated nitrogen precursor with partial or notemporal overlap between the different gas pulses.

The process 720 includes, in step 722, exposing a substrate toga gaspulse containing a metal precursor and optionally an inert gas such asAr. In step 724, the substrate is exposed to a gas pulse containing anitrogen precursor activated by a plasma source at a first level ofplasma power. In step 726, the substrate is exposed to a gas pulsecontaining a silicon precursor. In step 728, the substrate is exposed toa gas pulse containing the nitrogen precursor activated by the plasmasource at a second level of plasma power. As described above, FIGS. 5Aand 5B show power graphs depicting different levels of plasma powercoupled to a process chamber in accordance with embodiments of theinvention. In one example the first and second levels of plasma powercan monotonically increase or decrease during deposition of a metalsilicon nitride film that contains multiple metal layers and siliconlayers. In another example, the first and second levels of plasma powercan have different starting levels and vary independently of each otheror vary in a similar manner during deposition of the metal siliconnitride film. The first and second levels of plasma power may beselected and optimized for specific metal, silicon, and nitrogenprecursors and desired film properties.

The steps 722-728 may be repeated a predetermined number of times asshown by the process flow 734 until a strained metal silicon nitridefilm with a desired thickness has been deposited onto the substrate. Theprocess chamber may be purged with an inert gas, evacuated, or bothpurged and evacuated after each of steps 722, 724, 726, and 728.

According to one embodiment, steps 722 and 724 may be sequentiallyperformed a first number of times as shown by the process flow 730,prior to performing steps 726 and 728.

According to another embodiment, steps 726 and 728 may be sequentiallyperformed a second number of times as shown by the process flow 732,prior to repeating steps 722 and 724 in the process flow 734.

According to yet another embodiment, steps 722 and 724 may besequentially performed a first number of times prior to performing steps726 and 728 as shown by the process flow 730, and steps 726 and 728 maybe sequentially performed a second number of times as shown by theprocess flow 732, prior to repeating steps 722 and 724 in the processflow 734.

According to one embodiment, the first number of times may decreasemonotonically and the second number of times may increase monotonicallyeach time process flow 734 is performed. In one example, in step 722,the substrate is exposed to a gas pulse containing a metal precursor, instep 724, the substrate is exposed to a gas pulse containing a nitrogenprecursor activated by a plasma source at a first level of plasma power,and steps 722 and 724 are repeated twice using the process flow 730.Thereafter, in step 726, the substrate is exposed to a gas pulsecontaining a silicon precursor, and in step 728, the substrate isexposed to a gas pulse containing the nitrogen precursor activated bythe plasma source at a second level of plasma power. Next, in step 722,the substrate is exposed to a gas pulse containing the precursor, instep 724, the substrate is exposed to a gas pulse containing thenitrogen precursor activated by the plasma source at the first level ofplasma power, and steps 722 and 724 are repeated once using the processflow 730. Thereafter, in step 726, the substrate is exposed to a gaspulse containing the silicon precursor, in step 728, the substrate isexposed to a gas pulse containing the nitrogen precursor activated bythe plasma source at a first level of plasma power, and steps 726 and728 are repeated once using the process flow 732. Next, in step 722, thesubstrate is exposed to a gas pulse containing the metal precursor, andin step 724, the substrate is exposed to a gas pulse containing thenitrogen precursor activated by the plasma source at the first level ofplasma power. Thereafter, in step 726, the substrate is exposed to a gaspulse containing the silicon precursor, in step 728, the substrate isexposed to a gas pulse containing the nitrogen precursor activated bythe plasma source at the second level of plasma power, and steps 726 and728 are repeated twice using process flow 732. In this example, thefirst number of times decreases from 3 to 2 to 1 and the second numberof times increases from 1 to 2 to 3 during deposition of the strainedmetal silicon nitride film. In one example, the nitrogen precursor canbe selected from NH₃ and N₂H₄.

Still referring to FIG. 7B, according to one embodiment of theinvention, the gas pulse in step 724 may further comprise a dilution gasin a first ratio with the nitrogen precursor, and step 728 may furthercomprise the dilution gas in a second ratio with the nitrogen precursor,where the second ratio is different from the first ratio. The additionof a dilution gas to a nitrogen precursor can affect the plasma densityin the process chamber and thus the amount of activated nitrogenprecursor available to interact with the metal precursor. The dilutiongas may be selected from He, Ar, Ne, Kr, Xe, H₂, or N₂, or a combinationof two or more thereof. The first ratio may, for example, be defined asD/N or D/(D+N), where D and N refer to the amounts of the dilution gasand the nitrogen precursor, respectively. According to one embodiment,the first ratio may be varied from ratio corresponding to asubstantially pure nitrogen precursor, to another ratio corresponding toa combination of the dilution gas and the nitrogen precursor, to yetanother ratio corresponding to substantially pure dilution gas. In oneexample, a ratio D/(D+N) may increase monotonically as 0, 0.05, 0.10, .. . , 0.90, 0.95, and 1.0, during deposition of the metal siliconnitride film.

FIG. 7C is a process flow diagram for forming a strained metal siliconnitride film according to another embodiment of the present invention.The process 740 includes, in step 742, selecting a level of plasmapower. The level of plasma power can range from a first level at orbelow a lower limit for plasma formation to a second level of plasmapower corresponding to a maximum desired level of plasma power. Thus,the first level of plasma power can be 0 W of plasma power. In step 744,the substrate is exposed to a gas pulse containing a metal precursor, instep 746, the substrate is exposed to a gas pulse containing a siliconprecursor, and in step 748, the substrate is exposed to a gas pulsecontaining a nitrogen precursor activated by the plasma source at theselected level of plasma power. In step 750, the level of plasma poweris adjusted, and step 744 is repeated as shown by the process flow 752.According to one embodiment, the level of plasma power can monotonicallyincrease or decrease during deposition of the metal silicon nitridefilm. The process 740 may be performed as a pulsed PECVD process thatincludes interrupted gas exposures of a metal precursor, a siliconprecursor, and a plasma activated nitrogen precursor with at leastpartial temporal overlap of the gas pulses in steps 744, 746, and 748.Alternately, the process 740 may be performed as a PEALD process with nooverlap of the gas pulses in steps 744, 746, and 748.

Still referring to FIG. 7C, according to one embodiment of theinvention, the gas pulse in step 748 may further comprise a dilution gasin a first ratio with the nitrogen precursor, and step 750 may furthercomprise adjusting the amount of dilution gas from the first ratio to asecond ratio different from the first ratio.

FIG. 7D is a process flow diagram for forming a strained metal siliconnitride film according to another embodiment of the invention. Theprocess 760 includes, in step 762, exposing a substrate to a gas pulsecontaining a metal precursor, a silicon precursor, and a nitrogenprecursor activated by a plasma source at a first level of plasma power.In step 764, the substrate is exposed to a gas pulse containing themetal precursor, the silicon precursor and the nitrogen precursoractivated by the plasma source at a second level of plasma powerdifferent from the first level of plasma power. According to oneembodiment of the invention, the gas pulse in step 762 may furthercomprise a dilution gas in a first ratio with the nitrogen precursor andstep 764 may further comprise the dilution gas in a second ratio withthe nitrogen precursor, where the second ratio is different from thefirst ratio.

FIG. 7E is a process flow diagram for forming a strained metal siliconnitride film according to another embodiment of the present invention.The process 780 includes, in step 782, exposing a substrate to a gascontaining a metal precursor, a silicon precursor, and a nitrogenprecursor activated by a plasma source at a level of plasma power thatis varied during the exposure. In one example the level of plasma powercan monotonically increase or decrease during deposition of the metalsilicon nitride film. According to one embodiment of the invention, thegas pulse in step 782 may further comprises a dilution gas in a ratiowith the nitrogen precursor where the ratio is varied during theexposure. In one example the ratio can monotonically increase ordecrease during deposition of the metal silicon nitride film.

While the invention has been illustrated by the description of severalembodiments thereof, and while the embodiments have been described inconsiderable detail, they are not intended to restrict or in any waylimit the scope of the appended Claims to such detail. Additionaladvantages and modifications will readily appear to those skilled in theart. The invention in its broader aspects is therefore not limited tothe specific details, representative systems and method and illustrativeexamples shown and described. Thus, different aspects of the embodimentsdisclosed herein may be used in combination. For example, a metalnitride and a metal silicon nitride can alternately be formed in thesame deposition process, plasma and non-plasma steps can be included inthe deposition process etc. Accordingly, departures may be made fromsuch details without departing from the scope of the general inventiveconcept.

1. A method of depositing a strained metal silicon nitride film on asubstrate in a process chamber, comprising: exposing the substrate to agas comprising a metal precursor; exposing the substrate to a gascomprising a silicon precursor; exposing the substrate to a gascomprising a nitrogen precursor activated by a plasma source at a firstlevel of plasma power and configured to react with the metal precursoror the silicon precursor with a first reactivity characteristic; andexposing the substrate to a gas comprising the nitrogen precursoractivated by the plasma source at a second level of plasma powerdifferent from the first level and configured to react with the metalprecursor or the silicon precursor with a second reactivitycharacteristic such that a property of the metal silicon nitride filmformed on the substrate changes to provide the strained metal siliconnitride film, wherein the exposing the substrate to a gas comprising anitrogen precursor activated by a plasma source at a first level ofplasma power further comprises providing a dilution gas in a firstdilution ratio with the nitrogen precursor, and wherein the exposing thesubstrate to a gas comprising the nitrogen precursor activated by theplasma source at a second level of plasma power further comprisesproviding the dilution gas in a second dilution ratio with the nitrogenprecursor different from the first dilution ratio.
 2. The method ofclaim 1, comprising: a) exposing the substrate to a gas pulse comprisingthe metal precursor; b) exposing the substrate to a gas pulse comprisingthe nitrogen precursor activated by the plasma source at the first levelof plasma power; c) exposing the substrate to a gas pulse comprising thesilicon precursor; d) exposing the substrate to a gas pulse comprisingthe nitrogen precursor activated by the plasma source at the secondlevel of plasma power; and e) repeating steps a) - d) a predeterminednumber of times.
 3. The method of claim 2, further comprisingsequentially performing steps a) and b) a first number of times prior toperforming steps c) and d).
 4. The method of claim 2, further comprisingsequentially performing steps c) and d) a second number of times priorto repeating steps a) and b) in step e).
 5. The method of claim 2,further comprising sequentially performing steps a) and b) a firstnumber of times prior to performing steps c) and d), and sequentiallyperforming steps c) and d) a second number of times prior to repeatingsteps a) and b) in step e).
 6. The method of claim 2, wherein the firstlevel of plasma power or the second level of plasma power, or both firstand second levels of plasma power, are varied during deposition ofstrained metal silicon nitride film.
 7. The method of claim 6, whereinthe first and second levels of plasma power are between a first value ofplasma power at or below a lower limit for plasma formation and a secondvalue of plasma power corresponding to a maximum desired plasma power.8. The method of claim 2, further comprising purging or evacuating, orboth purging and evacuating the process chamber after each of stepsa)-d).
 9. The method of claim 2, wherein steps a) and b) have at leastpartial temporal overlap.
 10. The method of claim 2, wherein steps c)and d) have at least partial temporal overlap.
 11. The method of claim2, wherein steps a) and b) have at least partial temporal overlap andsteps c) and d) have at least partial temporal overlap.
 12. The methodof claim 1, wherein the metal precursor comprises elements selected fromalkaline earth elements, rare earth elements, Group III, Group IIIB,Group IVB, Group VB, and Group VIB of the Periodic Table, or acombination of two or more thereof.
 13. The method of claim 1, whereinthe nitrogen precursor is selected from N₂, NH₃, N₂H₄, and C₁-C₁₀ alkylhydrazine compounds.
 14. The method of claim 1, wherein the siliconprecursor comprises silane (SiH₄), disilane (Si₂H₆), monochlorosilane(SiClH₃), dichiorosilane (SiH₂Cl₂), trichiorosilane (SiHCl₃),hexachiorodisilane (Si₂Cl₆), diethylsilane, alkylaminosilane compounds,or a combination of two or more thereof.
 15. The method of claim 14,wherein the alkylaminosilane comprises di-isopropylaminosilane,bis(tert-butylamino)silane, tetrakis(dimethylamino)silane,tetrakis(ethylmethylamino)silane, tetrakis(diethylamino)silane,tris(dimethylamino)silane, tris(ethylmethylamino)silane,tris(diethylamino)silane, or tris(dimethylhydrazino)silane, or acombination of two or more thereof.
 16. The method of claim 1, whereinthe dilution gas is selected from He, Ar, Ne, Kr, Xe, H₂, or N₂, or acombination of two or more thereof
 17. The method of claim 1, whereinthe first and second levels of plasma power are between a first value ofplasma power at or below a lower limit for plasma formation and a secondvalue of plasma power corresponding to a maximum desired plasma power.18. The method of claim 1, comprising: exposing the substrate to a firstgas pulse comprising the metal precursor and the nitrogen precursoractivated by the plasma source at the first level of plasma power; andexposing the substrate to a second gas pulse comprising the siliconprecursor and the nitrogen precursor activated by the plasma source atthe second level of plasma power, wherein the first level or the secondlevel, or both the first and second levels are varied during thedeposition of the strained metal silicon nitride film.
 19. The method ofclaim 18, wherein the first gas pulse further comprises a siliconprecursor and the second gas pulse further comprises a metal precursor.20. The method of claim 1, wherein the first level or the second level,or both the first and second levels, are varied monotonically.
 21. Themethod of claim 1, wherein the exposing steps have at least partialtemporal overlap.